These two brothers are Co-Kings of the Denver Zoo Pride.
According to experienced feline zoo keepers, it is not unusual for brothers to share a pride while a lion stranger moving in would be the cause of a fight to the death with the victor winning the entire pride of lionesses. These two seemed quite comfortable with their shared position--and the pride is growing. This year alone we've gained 5 cubs.
As with all wild animals born in captivity, their genetic history is carefully recorded by the American Association of Zoos and Aquariums and if any animal's genes become over-represented in the total captive gene-pool, the animal is either vasectomized or norplanted depending on the gender. We once had a sign in our zoo that read, "computer Dating--Your zoo or mine?" Apparently some parents did not like this explanation of the Species Survival Plan so the sign was retired, though thankfully the plan survives.
Our zoo frequently receives "animals on loan" from other zoos for the purpose of infusing our captive populations with genetic variety. It certainly beats capturing them from the wild. Unfortunately animals are still confiscated from poachers, and if, for some reason, it is not possible to return them to the wild, they become another source of gene variance.
I do so love the big cats and I support whatever can be done to insure they will not become extinct on the planet.